1. Field of Invention
The present invention is related to an electro-photographic type image forming apparatus.
2. Description of Related Art
As this sort of image forming apparatus, such an image forming apparatus is known in which while a recording medium is transported along a substantially vertical direction, an image is formed on this transported recording medium, and then, the recording medium on which the image has been formed is ejected to an ejection unit provided on an upper portion of a main body of this image forming apparatus as disclosed in JP-A-10-207160.
The above-described prior art is represented in FIG. 6. In this prior art, a recording medium which has been transported from a paper supply unit 200 by a transport roller 202 is traveled through a transport path 204 which is formed along a substantially vertical direction, and an image is formed on this recording medium by an image forming section 206, and then, this recording medium on which the image has been formed is ejected to an ejection unit 210 which is formed at an upper portion of a main body 208 of the image forming apparatus. The image forming section 206 contains an image carrier 212 constructed of a photosensitive member, a charging apparatus 214 for charging this image carrier 212, an optical writing apparatus 216, a developing apparatus 218, a transferring apparatus 200, a cleaning apparatus 222, and also a fixing apparatus 224. The charging apparatus 214 charges this image carrier 212. The optical writing apparatus 216 forms a latent image on the image carrier 214 charged by this charging apparatus 214. The developing apparatus 218 develops the latent image of the image carrier 214 formed by this optical writing apparatus 216 so as to produce a visible toner image. The transferring apparatus 218 transfers the toner image of the image carrier 214 developed by this developing apparatus 218 onto the recording medium. The cleaning apparatus 222 is constituted by a blade for cleaning developer left on the image carrier 214. The fixing apparatus 224 fixes the toner image which has been transferred onto the recording medium.
The optical writing apparatus 216 is constituted by a scanning type laser exposing apparatus, and is arranged on the side of the developing apparatus 218. In this prior art, when reliability is taken into account, it is preferable to arrange the optical writing apparatus 216 along a horizontal direction. However, since this optical writing apparatus 216 is arranged along an oblique direction, such a device capable of reducing a width of this optical writing apparatus 216 along forward/backward directions (namely, right/left directions as viewed in FIG. 6) can be made.
However, in such a type of image forming apparatus that the recording medium is transported along the substantially vertical direction, dead spaces 226 and 228 are formed at both upper/lower portions of the optical writing apparatus 216 within the ejection unit 210 provided at the upper portion of this image forming apparatus. In other words, since the developing apparatus 218 is arranged at a position lower than a latent image writing position “P” where the latent image is written onto the image carrier 212 by the optical writing apparatus 216, the optical writing apparatus 216 must be arranged above the developing apparatus 218. As a result, the dead space 226 is formed between the ejection unit 210 and the optical writing apparatus 216, and also, the dead space 228 is formed between the optical writing apparatus 216 and the paper supply unit 200.
Moreover, conventionally, an image is transferred onto the image carrying body, while transporting the recording sheet in the substantially vertical direction, and scanning light is laterally incident on the image carrying body.
In this case, a toner replenishment box is disposed in downstream (in a lower part in this instance) of a latent image writing position on the image carrying body. Accordingly, the toner replenishment box does not hinder the operation of writing the latent image onto the image carrying body.
However, in this type of technique, the toner replenishment box is disposed in downstream (in a lower part in this instance) of a scanning light incident position. Therefore, for example, when the amount of toner is increased, the toner amount increase more easily affects the positions of a sheet tray and the optical unit, which are disposed in the lower part, since the volume of the toner replenishment box is increased. Changes to the specification of the machine, caused by the toner replenishing amount change, are not uniform. This makes it difficult to use the image forming apparatus in common for different specifications. An additional problem is that with increase of the toner replenishing amount, the machine size tends to increase.
Further, in a case where the machine is designed so as to allow the toner replenishment box to be pulled out from an upper part of the machine body, it entails that it is difficult to install another device in an upper space of the toner replenishment box. An additional technical problem arises that a dead space is easy to be formed in upstream (in an upper part in this instance) of the scanning light incident position.
Particularly in a case where the process cartridge is equipped with the toner replenishment box, such a technical problem is more remarkable by the amount of its occupied space increase.